Extracellular matrix (ECM) is a complex mixture of proteoglycans that function in cell adhesion, migration, growth and differentiation. In addition, the ECM serves as a reservoir for a number of growth factors, proteinases and proteinase inhibitors essential for ECM homeostasis. Our studies have shown that one of the serine proteinase inhibitors found in the ECM is a 32 kDa glycoprotein consisting of three tandemly- arranged Kunitz-type proteinase inhibitor domains homologous to tissue factor pathway inhibitor, an important negative regulator of blood coagulation. This novel inhibitor, designated as type-2 tissue factor pathway inhibitor, or TFPI-2, in synthesized and secreted into the ECM by endothelial cells, smooth muscle cells, fibroblasts, keratinocytes and urothelium. TFPI-2 readily inhibits several serine proteinase in vitro, strongly inhibited the trypsin or plasmin-mediated activation of promatrix metalloproteinases, and suppressed production of active MMP-2 in tumor cells transfected with the TFPI-2 expression vector. In addition, TFPI-2 expression is up regulated in human atherosclerotic coronary arteries, and its expression in solid tumors inversely correlates with the degree of malignancy. Thus, ECM-associated TFPI-2 may play a pivotal role in the regulation of ECM remodeling, a process essential for angiogenesis, atherogenesis and tumor invasion. The purpose of the studies proposed in this application is to examine in greater detail structure-function relationships in TFPI-2, its inhibitory properties in association with ECM structural proteins, and its role in tumor growth, vascularization and metastasis. Our preliminary data also show that TFPI-2 inhibits mononuclear cell transepithelial migration into airways in a murine model of allergic asthma, and studies are proposed to investigate its mechanism of action in this setting. The long range objectives of this proposal are to accomplish a comprehensive characterization of TFPI-2 in order to delineate its biological role in normal and pathological ECM turnover.